Molybdenum-Silicon-Boron (Mo—Si—B) is known in the prior art. It is being investigated for use in high temperature applications such as aircraft engines. When mixed in the proper ratios and heated to high temperatures these elements of molybdenum, silicon, and boron form three phases. Mo3Si and Mo5SiB2 (referred to by those of skill in the metallurgical and ceramic arts as A15 and T2 respectively) are the hard phases interspersed in an essentially molybdenum phase. Because of the solubility of silicon in molybdenum at high temperatures, the molybdenum phase is actually a solid solution between the molybdenum and silicon, referred to as molybdenum solid solution or Moss.
Mo—Si—B is useful in high temperature applications, including high temperature oxygen rich applications. When Mo—Si—B compositions are subjected to heat in air or substantially oxygen atmosphere, the T2 and A15 form a protective borosilicate glass on the exterior of the material. This glassy layer protects the Moss from oxidizing and volatilizing in air. However Mo—Si—B has limited application because the Moss phase is brittle at temperatures below 1000° C. To be useful for many applications the material must be ductile at room temperature. By reducing the amount of silicon present in the Moss the ductile to brittle transition temperature may be reduced, thus allowing the material to be ductile at lower temperatures, including room temperature.
Typically silicon and molybdenum form a solid solution during processing at high temperature. This begins to occur at temperatures above about 1300° C. As temperature increases above 1300° C., the amount of silicon in the solid solution increases. Typical melt processes require temperatures in excess of 1600° C. This introduces several atomic percent of silicon into the Moss which results in a high ductile to brittle transition temperature (1000° C.-1100° C. as described above). Disclosed in this patent is a low temperature process which substantially reduces the amount of silicon in the Moss phase, thus allowing for low temperature ductility.